A buddy informed me this weekend that a coach in our old pony league was hit in the temple by a ball during mid-inning infield warm-up. As reported to me, the coach dropped immediately (and then hit his head again). Last I heard, his post-surgery (crainiotomy) condition remains extremely serious.
With all the balls flying around pre-game and during games (be it tee-ball or high school age), I'm surprised this doesn't happen more often. We all routinely see foul ball near misses with toddlers and others. Seems like the "head's up" warning sometimes does more harm than good with many spectators (looking up versus covering their head).
I guess at a minimum, it's a good reminder to be vigilant when on or around a field.